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Date: Tue, 18 Aug 2020 13:45:29 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: axboe@...nel.dk
Cc: ming.lei@...hat.com, hch@....de, baolin.wang@...ux.alibaba.com,
baolin.wang7@...il.com, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] block: Add a new helper to attempt to merge a bio
There are lots of duplicated code when trying to merge a bio from
plug list and sw queue, we can introduce a new helper to attempt
to merge a bio, which can simplify the blk_mq_bio_list_merge()
and blk_attempt_plug_merge().
Meanwhile move the blk_mq_bio_list_merge() into blk-merge.c and
rename it as a generic name.
Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
block/blk-merge.c | 101 +++++++++++++++++++++++++++++++++++--------------
block/blk-mq-sched.c | 52 ++-----------------------
block/blk.h | 23 ++++++++---
block/kyber-iosched.c | 2 +-
include/linux/blk-mq.h | 2 -
5 files changed, 95 insertions(+), 85 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 3619f2f..6868961 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -900,13 +900,14 @@ static void blk_account_io_merge_bio(struct request *req)
part_stat_unlock();
}
-bool bio_attempt_back_merge(struct request *req, struct bio *bio,
- unsigned int nr_segs)
+enum bio_merge_status bio_attempt_back_merge(struct request *req,
+ struct bio *bio,
+ unsigned int nr_segs)
{
const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
if (!ll_back_merge_fn(req, bio, nr_segs))
- return false;
+ return BIO_MERGE_FAILED;
trace_block_bio_backmerge(req->q, req, bio);
rq_qos_merge(req->q, req, bio);
@@ -921,16 +922,17 @@ bool bio_attempt_back_merge(struct request *req, struct bio *bio,
bio_crypt_free_ctx(bio);
blk_account_io_merge_bio(req);
- return true;
+ return BIO_MERGE_OK;
}
-bool bio_attempt_front_merge(struct request *req, struct bio *bio,
- unsigned int nr_segs)
+enum bio_merge_status bio_attempt_front_merge(struct request *req,
+ struct bio *bio,
+ unsigned int nr_segs)
{
const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
if (!ll_front_merge_fn(req, bio, nr_segs))
- return false;
+ return BIO_MERGE_FAILED;
trace_block_bio_frontmerge(req->q, req, bio);
rq_qos_merge(req->q, req, bio);
@@ -947,11 +949,12 @@ bool bio_attempt_front_merge(struct request *req, struct bio *bio,
bio_crypt_do_front_merge(req, bio);
blk_account_io_merge_bio(req);
- return true;
+ return BIO_MERGE_OK;
}
-bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
- struct bio *bio)
+enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
+ struct request *req,
+ struct bio *bio)
{
unsigned short segments = blk_rq_nr_discard_segments(req);
@@ -969,10 +972,39 @@ bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
req->nr_phys_segments = segments + 1;
blk_account_io_merge_bio(req);
- return true;
+ return BIO_MERGE_OK;
no_merge:
req_set_nomerge(q, req);
- return false;
+ return BIO_MERGE_FAILED;
+}
+
+static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
+ struct request *rq,
+ struct bio *bio,
+ unsigned int nr_segs,
+ bool sched_allow_merge)
+{
+ if (!blk_rq_merge_ok(rq, bio))
+ return BIO_MERGE_NONE;
+
+ switch (blk_try_merge(rq, bio)) {
+ case ELEVATOR_BACK_MERGE:
+ if (!sched_allow_merge ||
+ (sched_allow_merge && blk_mq_sched_allow_merge(q, rq, bio)))
+ return bio_attempt_back_merge(rq, bio, nr_segs);
+ break;
+ case ELEVATOR_FRONT_MERGE:
+ if (!sched_allow_merge ||
+ (sched_allow_merge && blk_mq_sched_allow_merge(q, rq, bio)))
+ return bio_attempt_front_merge(rq, bio, nr_segs);
+ break;
+ case ELEVATOR_DISCARD_MERGE:
+ return bio_attempt_discard_merge(q, rq, bio);
+ default:
+ return BIO_MERGE_NONE;
+ }
+
+ return BIO_MERGE_FAILED;
}
/**
@@ -1011,8 +1043,6 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
plug_list = &plug->mq_list;
list_for_each_entry_reverse(rq, plug_list, queuelist) {
- bool merged = false;
-
if (rq->q == q && same_queue_rq) {
/*
* Only blk-mq multiple hardware queues case checks the
@@ -1022,26 +1052,41 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
*same_queue_rq = rq;
}
- if (rq->q != q || !blk_rq_merge_ok(rq, bio))
+ if (rq->q != q)
continue;
- switch (blk_try_merge(rq, bio)) {
- case ELEVATOR_BACK_MERGE:
- merged = bio_attempt_back_merge(rq, bio, nr_segs);
- break;
- case ELEVATOR_FRONT_MERGE:
- merged = bio_attempt_front_merge(rq, bio, nr_segs);
- break;
- case ELEVATOR_DISCARD_MERGE:
- merged = bio_attempt_discard_merge(q, rq, bio);
- break;
- default:
+ if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == BIO_MERGE_OK)
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * Iterate list of requests and see if we can merge this bio with any
+ * of them.
+ */
+bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
+ struct bio *bio, unsigned int nr_segs)
+{
+ struct request *rq;
+ int checked = 8;
+
+ list_for_each_entry_reverse(rq, list, queuelist) {
+ if (!checked--)
break;
- }
- if (merged)
+ switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
+ default:
+ case BIO_MERGE_NONE:
+ continue;
+ case BIO_MERGE_OK:
return true;
+ case BIO_MERGE_FAILED:
+ return false;
+ }
}
return false;
}
+EXPORT_SYMBOL_GPL(blk_bio_list_merge);
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index a19cdf1..5e63ede 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -359,7 +359,7 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
case ELEVATOR_BACK_MERGE:
if (!blk_mq_sched_allow_merge(q, rq, bio))
return false;
- if (!bio_attempt_back_merge(rq, bio, nr_segs))
+ if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
return false;
*merged_request = attempt_back_merge(q, rq);
if (!*merged_request)
@@ -368,14 +368,14 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
case ELEVATOR_FRONT_MERGE:
if (!blk_mq_sched_allow_merge(q, rq, bio))
return false;
- if (!bio_attempt_front_merge(rq, bio, nr_segs))
+ if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
return false;
*merged_request = attempt_front_merge(q, rq);
if (!*merged_request)
elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
return true;
case ELEVATOR_DISCARD_MERGE:
- return bio_attempt_discard_merge(q, rq, bio);
+ return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
default:
return false;
}
@@ -383,50 +383,6 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
/*
- * Iterate list of requests and see if we can merge this bio with any
- * of them.
- */
-bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
- struct bio *bio, unsigned int nr_segs)
-{
- struct request *rq;
- int checked = 8;
-
- list_for_each_entry_reverse(rq, list, queuelist) {
- bool merged = false;
-
- if (!checked--)
- break;
-
- if (!blk_rq_merge_ok(rq, bio))
- continue;
-
- switch (blk_try_merge(rq, bio)) {
- case ELEVATOR_BACK_MERGE:
- if (blk_mq_sched_allow_merge(q, rq, bio))
- merged = bio_attempt_back_merge(rq, bio,
- nr_segs);
- break;
- case ELEVATOR_FRONT_MERGE:
- if (blk_mq_sched_allow_merge(q, rq, bio))
- merged = bio_attempt_front_merge(rq, bio,
- nr_segs);
- break;
- case ELEVATOR_DISCARD_MERGE:
- merged = bio_attempt_discard_merge(q, rq, bio);
- break;
- default:
- continue;
- }
-
- return merged;
- }
-
- return false;
-}
-EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge);
-
-/*
* Reverse check our software queue for entries that we could potentially
* merge with. Currently includes a hand-wavy stop count of 8, to not spend
* too much time checking for merges.
@@ -440,7 +396,7 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
lockdep_assert_held(&ctx->lock);
- if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) {
+ if (blk_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) {
ctx->rq_merged++;
return true;
}
diff --git a/block/blk.h b/block/blk.h
index 49e2928..a180443 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -29,6 +29,12 @@ struct blk_flush_queue {
spinlock_t mq_flush_lock;
};
+enum bio_merge_status {
+ BIO_MERGE_OK,
+ BIO_MERGE_NONE,
+ BIO_MERGE_FAILED,
+};
+
extern struct kmem_cache *blk_requestq_cachep;
extern struct kobj_type blk_queue_ktype;
extern struct ida blk_queue_ida;
@@ -169,14 +175,19 @@ static inline void blk_integrity_del(struct gendisk *disk)
unsigned long blk_rq_timeout(unsigned long timeout);
void blk_add_timer(struct request *req);
-bool bio_attempt_front_merge(struct request *req, struct bio *bio,
- unsigned int nr_segs);
-bool bio_attempt_back_merge(struct request *req, struct bio *bio,
- unsigned int nr_segs);
-bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
- struct bio *bio);
+enum bio_merge_status bio_attempt_front_merge(struct request *req,
+ struct bio *bio,
+ unsigned int nr_segs);
+enum bio_merge_status bio_attempt_back_merge(struct request *req,
+ struct bio *bio,
+ unsigned int nr_segs);
+enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
+ struct request *req,
+ struct bio *bio);
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
unsigned int nr_segs, struct request **same_queue_rq);
+bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
+ struct bio *bio, unsigned int nr_segs);
void blk_account_io_start(struct request *req);
void blk_account_io_done(struct request *req, u64 now);
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index a38c5ab..6d4ba0e 100644
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -573,7 +573,7 @@ static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
bool merged;
spin_lock(&kcq->lock);
- merged = blk_mq_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
+ merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
spin_unlock(&kcq->lock);
return merged;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 9d2d5ad..21a02e0 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -489,8 +489,6 @@ static inline int blk_mq_request_completed(struct request *rq)
void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs);
void blk_mq_complete_request(struct request *rq);
bool blk_mq_complete_request_remote(struct request *rq);
-bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
- struct bio *bio, unsigned int nr_segs);
bool blk_mq_queue_stopped(struct request_queue *q);
void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx);
--
1.8.3.1
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